The present invention relates to a pattern exposure method and system for forming a pattern by a combination of a reduction projection exposure system and an electron beam exposure system.
Recently semiconductor devices have been increasingly integrated, and sub-micron pattern rules are required. Pattern formation by the use of conventional reduction projection exposure systems will find it impossible to meet such rules. Pattern formation by means of a combination of exposure systems having principles different from each other, i.e., a reduction projection exposure system and an electron beam exposure system, has been again noted.
In a case that a pattern is formed by a combination of exposure systems of different principles from each other, i.e., a reduction projection exposure system and an electron beam exposure system, a problem is accuracy of positioning between patterns formed by the respective exposure systems.
For example, when a pattern is superimposed by the electron beam exposure system, ignoring optical strains caused by the reduction projection exposure system, positioning accuracy is deteriorated especially at a peripheral part of a semiconductor chip, with a result of positioning errors.
As conventional art for preventing positioning errors between a reduction projection exposure system and a charged particle beam exposure system, e.g., the electron beam exposure system, are known those described in Japanese Patent Laid-Open Publication No. 58621/1987 and Japanese Patent Laid-Open Publication No. 149127/1987. In these conventional art an amounts of an optical strain of the reduction projection exposure system is measured in advance by the charged particle beam exposure system, and when an actual pattern is exposed, corrections are made based on the pre-measured optical strain.
However, in the conventional art an optical strain amount caused by the reduction projection exposure system is measured by a charged particle beam exposure system, and a measured value advertently contains, in addition to an optical strain of the reduction projection exposure system, a productional error of a reticle and a measurement error of the electron beam exposure system. Accordingly, although positioning is performed based on a measured value of the electron beam exposure system, defective positioning of the reduction projection exposure system with respect to the electron beam exposure system cannot be effectively prevented.